Hepatitis C virus (HCV) is the major causative agent for most cases of non-A, non-B hepatitis. The virus is a single-stranded positive RNA virus in the Flaviviridae family. It includes a nucleocapsid protein (C), envelope proteins (E1 and E2), and several non-structural proteins (NS1, NS2, NS3, NS4a, NS5a, and NS5b). The NS3 protein possesses serine protease activity and is considered essential for viral replication and infectivity, and the essentiality of the NS3 protease was inferred from the fact that mutations in the yellow fever virus NS3 protease decreased viral infectivity [reference: Chamber et al, Proc. Natl. Acad. Sci. USA 87, 8898-8902 (1990).
So far, HCV infection is one of major human health problems since HCV infection leads to chronic liver disease such as cirrhosis and hepatocellular carcinoma. Due to the fact that the number of HCV infected individuals is estimated 2-15% of the world's population while no any effective vaccines or therapeutic agents are available to control or cure HCV [reference: WO 89/04669; Lavanchy, J. Viral Hepatitis, 6, 35-47 (1999); Alter, J. Hepatology, 31 (Suppl. 1), 88-91 (1999); and Alberti et al, J. Hepatology, 31 (Suppl. 1), 17-24 (1999)].
It has been demonstrated that mutations at the active site of the HCV NS3 protease completely inhibited the HCV infection in chimpanzee model [reference: Rice et al, J. Virol. 74 (4) 2046-51 (2000)]. Furthermore, the HCV NS3 serine protease has been found to facilitate proteolysis at the NS3/NS4a, NS4a/NS4b, NS4b/NS5a, NS5a/NS5b junctions and is thus responsible for generating four viral proteins during viral replication [reference: US 2003/0207861]. Consequently, the HCV NS3 serine protease enzyme is an attractive and effective target to develop new inhibitors for HCV infection. So far, there are different kinds of potential NS3 HCV protease inhibitors reported by global research institutes and pharmaceuticals, such as WO2010033466, WO2010075127, US20100003214, US20100022578, US20100029715, US20100041889, WO2009134624, WO2009010804, US20090269305, WO2008057209, WO2008057208, WO2007015787, WO2005037214, WO200218369, WO200009558, WO200009543, WO199964442, WO199907733, WO199907734, WO199950230, WO199846630, WO199817679, U.S. Pat. No. 5,990,276, Dunsdon et al, Biorg. Med. Chem. Lett. 10, 1571-1579 (2000); Llinas-Brunet et al, Biorg. Chem. Lett. 10, 2267-2270 (2000); and S. LaPlante et al., Biorg. Med. Chem. Lett. 10, 2271-2274 (2000).
Currently, due to lack of immunity or remission associated with HCV infection, hepatitis caused by HCV infection is more difficult to treat comparing to other forms of hepatitis. Now, the only available anti-HCV therapies are interferon-a, interferon-a/ribavirin combination, and pegylated interferon-a. However, sustained response rates for interferon-a or interferon-a/ribavirin combination were found to be <50% and patients suffer greatly from side effects of these therapeutic agents [reference: Walker, DDT, 4, 518-529 (1999); Weiland, FEMS Microbial. Rev., 14, 279-288 (1994); and WO 02/18369]. Based on the significant importance for controlling HCV infection, the aim of the present invention is to develop more effective and better-tolerated therapeutic drugs for inhibiting HCV NS3 protease replication.